320 Scientific Intelligence. 
Nautical Almanac, but were transferred to the Transit Commis- 
sion, who published them. The four large charts accompanying 
the paper are suited to the use of navigators who may wish to 
observe the transit. They are, we may observe, remarkably fine 
agora of map printing, the work, if we are ‘not mistaken, of 
. Bie 
8. ae the Auroral Spectrum.—A letter from Henry A. Rowland, 
at present Instructor in Physics in the Rensselaer Polytechnic 
Tnstitute at Troy, informs us that he observed the line of wave- 
length 431 in the auroral spectrum of last October. H 
“The observations were made with an posspapes chemical spec- 
troscope of one prism, in which the scale was read by means of a 
lamp. Great care was taken in the readings, and aioe completing 
them the pacipiireaiggs was set aside until morning, when the 
readings were taken sa lines of comparison without eee 
the instrument in e 8 or even regulating the slit. Thew 
lengths of the known lines were taken from Watts’s nies ‘et 
Spectra, > but as he does not give the wave-lengths of lines in the 
27°5, Ca 6 36°, Ca a6 95°5°, and K f 110°. ‘The aurora lines were 
as follows : 
Scale-reading, Wave-lengths, 
} 628°3 
Z 35°5 554°3 
3 95 425 
“The wave-lengths of the auroral lines were obtained by graphi- 
~ oe on such a lar ge scale as to introduce -_ or no 
"O. ieee on Encke’s Comet, and ~ reports from shee U. 8. 
Naval Vbservatory. —From Admiral Sands we have received at 
different times the 2d, 3d, and 4th re saad to the volume of 
observations for cee nade the 4th Appendix for the volume for 
1871, of the U. S. N ‘. Observatory, 
The 2d ‘Appendix consists of reports by Professors Hall and 
Harkness on Observations of Encke’s Comet during its return in 
1871. Prof. Hall gives the positions of the comet, notes of its 
appearance, and fou ings 0 Prof. Harkness gives his 
observations upon the spectrum of the comet, followed by a dis- 
cussion of the probable mass of the comet, and the density of the 
— resisting medium of space. The following i is the general 
5 ary of his results: 
(1.) Eneke’s comet gives a carbon-spee 
(2.) From November 18th to pee = 2d the wave-length of 
the fbrightest part of the second band of the comet’s spectrum was 
continually increasin 
(3.) Sg polarization was detected in the light of the comet. 
(4.) The mass of Encke’s comet is certainly not less than that of 
an asteroi 
-. (5.) The density of the supposed resisting medium in space, 28 
" computed from the observed retardation of Encke’s comet, is such : 
